The tours are part of the National Heritage Open Days and offer an insight into the building’s rich history.
Visitors can explore the council chamber, old prison cells and more.
The building has been a grand mansion, tavern, magistrate’s court, police station and is now the premises of Thornbury Town Council.
This year’s Heritage Open Day theme is architecture and attendees can view rare drawings and illustrations showing the town hall’s evolution over time.
The tours will take place on Saturday, September 13, between 10am and 2pm.
No booking is necessary.
Heritage Open Days is England’s largest festival of history and culture, organised by the National Trust and supported by the People’s Postcode Lottery.
The event offers free access to various experiences and events across England, including sites that usually charge for admission.
For more details, visit the Heritage Open Days website.
